The Amp Garage

trying to determine how i might design a bias supply that reliably charges in tandem with, or before the HT supply, without the use of a DC Standby switch. ... Forget the HT supply, and focus on the heater warmup time (something like 10-25 seconds?). If the output tube heaters are cold, the cathode...

Guy just really, really wanted "675Ω" as the cathode resistor, and "25.5kΩ" as the dropping resistor for the screen filter cap?? I don't think the circuit-values are so critical, so the above doesn't make sense. Then again, providing the very-high dropping resistance to the screen node because of "p...

jabguit wrote: ↑Sat Oct 18, 2025 11:20 am I see orange-orange-green, which should be 3M3, no?

Thanks for the correction! I was reading the code backwards, because I didn't go to the other photo to notice that other Orange band.

I agree entirely! On another forum, someone was very concerned that their 1962 Fender amp didn't exactly match the voltage numbers on the schematic. They wanted to modify their amp to "get the voltages right." I tried to be as persuasive as possible to tell them, "Your amp is right, the schematic is...

Sag is contributed to current supply of the HT. Voltage affects the performance of the output stage. ... Sag is contributed to current supply of the HT. Voltage affects the performance of the output stage. More accurately, sag results when the amount of current pulled from the PT->rectifiers->filte...

... I would have thought the resistance/impedance of the meter would be quite high, at least high enough not to affect the voltage reading. The meter is an early 80’s Fluke 77, it still works so I wouldn’t throw it away. The input impedance of the Fluke 77 series 1 is 10M, I estimate that resistor ...

EDIT: mistaken post.

I put a new .02 coupling cap between the 12AX7 pin 6 and pin 5 of the 6V6 and no difference. ... Disconnect the 0.02µF cap entirely. Also do exactly what Sluckey advised here: That voltage should be zero volts. Pull the 6V6 and recheck the voltage on pin 5. If not zero, then disconnect that .02µF c...

Could anyone provide insight into this amp? It appears to be a 1963 fender twin black face with a single 15" speaker, JBL, that is centered. From my research, it appears that this is a prototype amp for steel guitar players. ... The top amp in your post is different from the bottom amp in your post...

Roe wrote: ↑Sat Sep 13, 2025 9:28 am 4 tubes sound better normally

I agree that an unmolested Twin Reverb sounds better normally.

But dude has an 8Ω reactive load, and a 4Ω Twin. If he wants to play, today, he can just yank 2 output tubes and have an "8Ω output Twin."

Not the same, but it is what it is.

I recently wanted to use a Fender Twin Reverb blackface reissue for reamping purposes and with reactive loads, but I soon noticed that it only has 4 ohm speaker outs whereas the two reactive loads that I use (Suhr Reactive Load / St. Rock React:IR) are both rated at 8 ohm. Pull 1 output tube from e...

Sorry to again be the dude that's pushing back... ... much of the fundamental “personality” of the amp can be distilled through more detailed design of the power section itself (assuming you get to turn it up enough to actually push the power section). Considering the type and “temperature” of bias ...

I've just built myself a 6G3 clone. ... On the fender diagram, it shows, 333-0-333 into a GZ34, with an output of 375V. ... Fender schematics are not Gospel . So you can't expect the numbers on them to exactly match the actual vintage amps. It also turns out that most modern power transformers don'...

The diagram includes the recommended heatsink for your regulator . I assumed bolting to the chassis would be a far better heatsink as it's much larger than that heatsink. Unfortunately, that's not true. Otherwise, we wouldn't have an industry that makes heatsinks of special material/shape that gets...

liddokun wrote: ↑Fri Sep 05, 2025 11:22 pm I'm powering 3 12ax7s.

I've got it bolted to the amp's chassis. The chassis gets mad hot as you've described as well.

The diagram includes the recommended heatsink for your regulator.